<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        body {
            position: relative;
        }

        .circle {
            position: absolute;
            width: 120px;
            height: 120ox;
            border-radius: 50%;
            background-color: yellow;
            animation: a 4s infinite;
        }

        @keyframes a {

            0 100% {
                transform: translate3d(0, 0, 0);
            }

            50% {
                transform: translate3d(120px, 0, 0);
            }

        }
    </style>
</head>

<body>
    <div class="circle">

    </div>
</body>

</html>